Among the works of art on the walls of Tabitha Simmons and Craig McDean’s town house in Manhattan’s Chelsea—the Andy Warhol shoe sketch, the Irving Penn skull photographs—is a sheet of construction paper divided into boxes titled hamster chart. “The boys have to do certain tasks to get a star. It encourages teamwork!” says Simmons, a former model who is currently a stylist and a sought-after shoe designer, explaining that her sons—Elliott, seven, and Dylan, six—are attempting to amass enough stars to earn a hamster, an eventuality that she and her photographer husband are approaching with less than rabid enthusiasm.

This rodent interloper, when he invariably escapes his cage, will have plenty of space to get lost. The five-story Queen Anne–style edifice, bought by the couple seven years ago, is now a stunning but relaxed showplace that combines Simmons’s love for an amusing, even whimsical detail and McDean’s obsession with any color palette as long as it is white. Or, as their architect, Annabelle Selldorf, put it: “One wants to blow out the back of the house; the other wants to grow wisteria up it.”

The result is a particularly happy mélange that can accommodate a huge cherub-bedecked carved-bone Victorian mirror in the master bedroom hanging next to a circa 1985 Tom Dixon Star Light paper ceiling lamp, and, in the bathroom, an eighteenth-century gilt, iron, and crystal chandelier over the bathtub illuminating a circa 1989 aluminum Mark Brazier-Jones Whaletail chair. The pristine McDean/Simmons refuge, with interiors designed by Virginia Tupker, was not always this paragon of family-friendly elegance. (Face it: Returning a Manhattan building that has been cut up into apartments to single family–home glory is never exactly two weeks in the Bahamas.) “The whole place was gutted—the only remnant of the 1850s was the front door,” Simmons recalls ruefully. “When we blew the back of the house out, I nearly had heart failure. At one point there was no back and no roof. It was completely run-down, and Craig made us live in it for a year while we drew up the plans! Dylan was the only six-month-old with his own apartment.” Though McDean at first envisioned unadulterated glass sheets for the entire rear of the house, Simmons insisted on panes. “It would have been like living in a goldfish bowl!”

Though she claims that she is never out of stilettos, today Simmons is shod in a pair of snowy Nikes for two reasons: (1) She has a tennis date and (2) McDean discourages, almost forbids, high heels in the house, lest they mar the dark walnut floors. If this is distressing to the designer, who is famous for her witty, vertiginous footwear, she shrugs and laughs, then offers to lead a visit to the basement, where what appear to be hundreds of pairs of shoes from her past—McQueen booties, Galliano high-steppers—currently reside. But this sojourn to cellar–as–shoe museum is interrupted by a cry that she is needed pronto in the playroom to help with a particularly knotty Lego problem. Elliott and Dylan, who insist they are completely and utterly finished with their homework, are ensconced in a cozy room with no TV or computer but lots of dinosaurs and board games and Hinson & Company wall­paper meant to look like random blue spatters. It is one of only two areas in the house with non-white walls, the other being the nanny’s room, a riot of Josef Frank Jungle Blue fabric, which stands in cheerful contradiction to the rest of the place. “Craig has difficulty with color in a room,” Simmons explains. “He’s creating images on a constant basis. He wants his home to be a clean palette—as if he’s setting a refresh button.”

An attempt to bribe the boys with hamster stars for a house tour is considered and then rejected (it is possible that when you are six and seven you are not exactly sure what a house tour is), so Simmons embarks on the task alone. Standing in the living room next to a glass dome containing an elaborate nineteenth-century folk-art shell sculpture known as a Sailor’s Valentine, she explains that she and McDean each retain veto power over interior decisions, a situation that once led Elliott to ask, “Mommy, why does the furniture keep going in and out of the house?” Happily, the couple have been able to compromise on such items as the pair of circa 1964 Gio Ponti lounge chairs (Craig adores them) and a huge butterfly rug specially made by the Rug Company (“I have an obsession with butterflies and dragonflies,” she confesses).

Simmons also admits that until recently, she paid far more for a dress than for a piece of furniture. “The first piece I ever bought was this Gallé Art Nouveau table. We found it in En­gland,” she says, gently caressing its seductive contours. Though many of the pieces were purchased from European auction houses, not everything has a foreign provenance. Outside the boys’ bedroom (they share because, well, there could be giant snakes or monsters in the garden) is a trio of skateboards designed by Takashi Murakami, Jeff Koons, and Damien Hirst, found at Supreme, a skateboard shop in SoHo, and framed.

Oddly, there is no guest room, but a small, semirenovated area with an outdoor balcony on the top floor on its way to becoming an office, sometimes accommodates a particularly glamorous overnight guest. “Before Karen Elson got a place in Manhattan, she used to sleep up here on an inflatable bed,” Simmons says. “I met her years ago in this very neighborhood. I used to see her all decked out in Chanel at the deli. I love Chelsea! It feels like a small community.”

A primitive plinking interrupts this reverie—Dylan is having a piano lesson. He likes his mom to hang out just outside the door when the teacher is here, so she can listen but not intrude upon the deadly serious proceedings. Simmons smiles indulgently, but when she takes a seat on the floor under the skateboard triptych, the sound of her six-year-old playing has brought tears to her eyes.